1. Field of the Invention
The present invention especially relates to a rodless cylinder in which head covers installed to ends of a cylinder tube are mutually exchangeable and commonly usable.
2. Description of the Related Art
In recent years, the rodless cylinder is adopted in various cases as an apparatus for transporting a workpiece in a factory or the like. The rodless cylinder makes it possible to shorten the entire length with respect to the displacement length as compared with a cylinder which has a rod. Therefore, the rodless cylinder occupies a small area, and it is conveniently handled, making it possible to perform, for example, highly accurate positioning operation.
As shown in FIG. 8, the rodless cylinder 1 concerning the conventional technique includes a cylinder tube 2, a slide table 3, and a pair of head covers 4, 5. The rodless cylinder 1 has two lines of passages 8, 9 for allowing the compressed fluid to flow therethrough. The respective head covers 4, 5 are provided with fluid pressure inlet/outlet ports 6a to 6f, 7a to 7f which serve as introducing ports for the compressed fluid.
A passage 8 for allowing the compressed fluid to flow communicates with the fluid pressure inlet/outlet ports 6a to 6f. Another passage 9 communicates with the fluid pressure inlet/outlet ports 7a to 7f. Further, the passages 8, 9 are conducted to the inside of the space in which an unillustrated piston, which is arranged at the inside of the cylinder tube 2, makes reciprocating movement. Any one of the fluid pressure inlet/outlet ports 6a to 6f and any one of the fluid pressure inlet/outlet ports 7a to 7f are provided on first principal surfaces of the respective head covers 4, 5.
In the case of the rodless cylinder 1, a pair of the fluid pressure inlet/outlet ports 6a, 7a are selected as ports for introducing/discharging the compressed fluid. Further, the other fluid pressure inlet/outlet ports 6b to 6f, 7b to 7f, which are not used, are closed by plug members.
The slide table 3 is moved linearly in the direction of the arrow A shown in FIG. 8 in accordance with the action of the supply of the compressed fluid supplied via the fluid pressure inlet/outlet port 6a. When the compressed fluid is supplied via the fluid pressure inlet/outlet port 7a, the slide table 3 is moved linearly in the direction of the arrow B shown in FIG. 8.
However, in the case of the rodless cylinder 1 concerning the conventional technique, as described above, each one of any one of the fluid pressure inlet/outlet ports 6a to 6f communicating with the passage 8 and any one of the fluid pressure inlet/outlet ports 7a to 7f communicating with the passage 9 is provided on each of the first principal surfaces of the respective head covers 4, 5. Therefore, the compressed fluid passages, which are formed at the inside of the head cover 4 and the head cover 5 respectively, are asymmetric with respect to the short side direction of the cylinder tube 2. For this reason, the head cover 4 and the head cover 5 are not mutually exchangeable, and they cannot be commonly used.
Therefore, for example, when the head covers are formed by using an injection molding machine, it is necessary to use two types of molds. Further, it is necessary to use jigs corresponding to the respective molds. Therefore, a problem is pointed out that the operation for adjusting the jig is complicated, and the production cost is expensive for the rodless cylinder as a whole.
Further, it is necessary that the two lines of the passages 8, 9, which are disposed at the inside of the cylinder tube 2, are defined in a separate manner respectively. An inconvenience arises such that the size of the rodless cylinder 1 in the height direction is large, and it is impossible to respond to the demand for realization of a small size. Further, the size of the rodless cylinder 1 is increased, and the installation space is enlarged.
A general object of the present invention is to provide rodless cylinder which makes it possible to miniaturize the rodless cylinder and reduce the installation space.
A principal object of the present invention is to provide a rodless cylinder which makes it possible to mold head covers of the rodless cylinder with a single mold.
Another object of the present invention is to provide a rodless cylinder which makes it possible to reduce the production cost of the rodless cylinder as a whole and which makes it possible to achieve a small size and a reduced installation space.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.